The present invention relates to a video display apparatus and method for displaying the power saving modes for use with a computer monitor.
In order to reduce power consumption, computer monitors have been designed having a power-save mode that is automatically selected after the monitor has been on, but not in use, for a long period of time. Industry standards have been developed, for example, the standard made by VESA (Video Electronics Standards Association) in the U.S.A., requiring a computer monitor to be operated in four power-save modes: "on-mode", "standby mode", "suspend mode" and "active-off mode". The on-mode is used when the computer monitor is displaying a picture, and the other modes are used when no picture is displayed. As the modes are changed under control of the computer from the on-mode, to the standby mode, to the suspend mode, and to the active-off mode, in that order, the number of operating circuits is reduced and the power consumption is lowered.
Each mode of the computer monitor is set under computer control based on the sync signals contained in a video signal supplied to the display apparatus. Specifically, when a horizontal sync signal and a vertical sync signal are transmitted together with a video signal, the display apparatus is placed in the on-mode, thereby displaying a picture based on the video signal.
When the horizontal sync signal is not transmitted and only the vertical sync signal is, the display apparatus is placed in the standby mode where most circuits are energized. In this mode, when the transmission of the video signal and the horizontal sync signal is resumed, the display apparatus is switched to the on-mode, thereby immediately resuming the display of a picture.
When the vertical sync signal is not transmitted and only the horizontal sync signal is transmitted, the computer monitor is placed in the suspend mode where only the heater of the cathode ray tube (CRT) and the circuits making up the control system are energized. In this mode, when transmission of the video signal and the vertical sync signal is resumed, the display apparatus is switched to the on-mode, thereby resuming the display of a picture in a relatively short period of time.
When neither the horizontal sync signal nor the vertical sync signal are transmitted, the computer monitor is placed in the active-off mode where only a minimum number of the circuits of the control system are energized. In this mode, when the transmission of the video signal and the sync signals are resumed, the display apparatus is switched to the on-mode, thereby resuming the display of a picture after a relatively long period of time.
Therefore, the power consumed when the display apparatus is not in use can be optimized by a plurality of power save modes. Also, once the computer monitor is placed in the active-off mode, it cannot be returned to the on-mode until the power-supply switch is operated.
Finally, the suspend mode is an optional mode in the above mentioned VESA standard. Only the on-mode, standby mode, and active-off modes are required modes.
A monitor having a plurality of power-save modes has to display its current operation mode. Since these power-save modes are used when a picture is not displayed, these power-save modes cannot be displayed pictorially on the picture screen. Therefore, the current operation mode of the computer monitor is displayed on a dedicated display unit including light-emitting diodes or a liquid-crystal panel.
Considering that the power-save modes are intended to lower power consumption, a minimum amount of power should be consumed in order to display their status. For example, a method for displaying power saving modes using four light-emitting diodes accomplishes a low power consumption since the four light-emitting diodes are provided for the four modes, only one of them is energized at a time.
If four light-emitting diodes are used solely to display the operation modes, however, the computer monitor design becomes complex. Also, since the computer monitor needs space for placing the four light-emitting diodes, the computer monitor becomes unnecessarily large in size.